The present invention relates to a method and apparatus for use in dilating occluded blood vessels. The invention is particularly concerned with such a method and apparatus wherein dilatation is achieved through means of a balloon element which is initially inverted within the distal end of a catheter and, in use, extruded through and expanded within the occlusion being treated. The invention is intended for use in treating either arterial or venous occlusions.
Prior art efforts for the treatment of occluded blood vessels have relied primarily upon the employment of bypass vessels or some surgical technique whereby the occlusion is physicially removed from the vessel being treated. Another recent technique for treating occluded vessels relies upon the insertion of some type of an instrument into the vessel to dilate the occlusion through a stretching or compressing process. The present invention is concerned with a technique of the latter type.
A principal problem with the employment of techniques wherein instruments are inserted into the vessel to effect dilatation by compression or stretching is that the instruments may damage the vessel and/or dislodge material therefrom. Another problem with such techniques is that it has been very difficult to place the instruments used therefor in highly occluded or small diameter vessels. These problems have resulted primarily from the construction and size of the instruments. In one such technique, the instruments take the form of progressively larger catheters which are successively forced through the vessel being treated. In another technique, the instruments have taken the form of an inflatable catheter which is forced into place within the occluded area to be treated and, once in place, inflated. These prior catheters, although flexible, are necessarily somewhat hard and inelastic, in order to enable the catheter to be advanced large distances through the arterial or venous systems. The inherent hardness of these catheters contribute to the problems of vessel damage and material dislodgement mentioned previously.